Cr Filament-Reinforced CrMnFeNiCu(Ag)-Based High-Entropy Alloy and Method for Manufacturing the Same

ABSTRACT

A Cr filament-reinforced CrMnFeNiCu(Ag)-based high-entropy alloy and a method for manufacturing the same are provided. The high-entropy alloy, according to an exemplary embodiment in the present disclosure, includes, by at. %, Cr in an amount greater than 5% and less than 42%, Mn in an amount greater than 5% and less than 35%, Fe in an amount greater than 5% and less than 35%, Ni in an amount greater than 5% and less than 35%, and at least one of Cu in an amount greater than 3% and less than 35%, and Ag in an amount greater than 3% and less than 35%, and residual inevitable impurities. The high-entropy alloy has a dual phase in which a Cr or a Cr-rich phase is distributed within a matrix of the high-entropy alloy in filament or ribbon form.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No.10-2017-0089095 filed Jul. 13, 2017, the disclosure of which is herebyincorporated in its entirety by reference.

BACKGROUND

The present disclosure relates to a method for manufacturing aCrMnFeNiCu-, CrMnFeNiAg-, or CrMnFeNiCuAg-based high-entropy alloy thatmay be used in materials for parts in the electromagnetic, chemical,shipbuilding, and machinery, and in engineering components andstructural materials employed in extreme and harsh environments, andmore particularly, to a method for manufacturing a Crfilament-reinforced CrMnFeNiCu(Ag)-based high-entropy alloy that mayprovide a plate material, a rod material, or a wiring material, whichmay be a Cr filament-reinforced CrMnFeNiCu-, CrMnFeNiAg-, orCrMnFeNiCuAg-based high-entropy alloy formed of an in-situ compositematerial.

High-entropy alloys may be alloys that reduce the overall level of freeenergy, since increases in the configuration entropy due to mixtures ofvarious elements are greater than decreases in free energy through theformation of intermetallic compounds, and may refer to alloys in which ametallic compound or an amorphous alloy, among multi-alloying elements,is not formed, but in which a solid solution having various alloyingelements mixed therein is preferentially formed.

In a published article, entitled: “Microstructural development inequiatomic multicomponent alloys” by B. Cantor, et al., appearing inMaterials Science & Engineering A, Vols. 375-377 (2004) pp. 213-218, thedisclosed high-entropy alloy is an alloy attracting interest since thealloy, Fe₂₀Cr₂₀Mn₂₀Ni₂₀Co₂₀, manufactured in expectation of formation ofan amorphous alloy or a complex intermetallic compound exhibits acrystalline face-centered cubic (FCC) solid solution, contrary toexpectations. By comparison with conventional alloys in which otheralloying elements are added to primary alloying elements of 60 to 90 at.%, the high-entropy alloy has a specific property that even whenalloying elements having a four or five or more element system are mixedat a similar ratio, a single phase is formed, and this is found inalloys having a higher level of configuration entropy due to mixing.

The high-entropy alloy is an alloying system containing four or moretypes of metallic elements of 5 to 35 at. %, all of the added alloyingelements acting as primary elements, and a high level of mixing entropymay be caused by similar atomic fractions within the alloy. Thus, asolid solution having a stable, simple structure may be formed at hightemperatures, in lieu of an intermetallic compound or an intermediatecompound.

US 2013/0108502 A1 discloses a high-entropy alloy that may achieve highlevels of hardness and modulus of elasticity and that may consist of asingle-phase solid solution having a FCC and/or body-centered cubic(BCC) structure as an alloying system that contains five or moremetallic elements as multiple metallic elements including respectiveelements of ±15 at. % or less, such as V, Nb, Ta, Mo, and Ti, and thathas all of the added elements acting as primary elements. However,patent document 1, as described above, includes various types ofrelatively expensive, heavy alloying elements added, and hasdifficulties in the manufacturing process due to the difference inmelting points among the added alloying elements.

Meanwhile, US 2009/0074604 A1 pertains to a high-entropy alloy that mayachieve a high level of hardness and that may be manufactured by apowder metallurgy process using a ceramic phase (typically, tungstencarbide) and a multiple element high-entropy alloy powder, and to atechnique for achieving excellent mechanical properties by forming thehigh-entropy alloy as a single-phase solid solution having a FCC and/orBCC structure reinforced with strong ceramic phase. However, when thealloy is manufactured using a ceramic-based material as in US2009/0074604 A1, it may be difficult to manufacture the alloy because ofthe requirement for a high-temperature process.

In recent years, apart from the manufacturing of a high-entropy alloyusing a single-phase solid solution, interest in a high-entropy alloyhaving a single phase matrix reinforced with a second phase isincreasing, and research taking advantage of the various strengtheningmechanisms, such as solid solution strengthening, precipitationhardening, and composite strengthening, has been extensively conducted.

SUMMARY

An aspect of the present disclosure may provide a high-entropy alloy inwhich a single-phase solid solution matrix and a Cr-rich phase,containing Cr as a main element, may be separately formed in an alloycomprising main elements, such as Cr, Mn, Fe, Ni, and Cu and/or Ag andwhich may have excellent levels of strength and ductility bydistributing the Cr-rich phase within the matrix through solidificationand thermo-mechanical processes and developing a filamentary structurethrough thermos-mechanical and deformation processes, and a method formanufacturing the high-entropy alloy with second phase reinforcement.

According to an aspect of the present disclosure, a high-entropy alloyincludes: by at. %, Cr in an amount greater than 5% and less than 42%,Mn in an amount greater than 5% and less than 35%, Fe in an amountgreater than 5% and less than 35%, Ni in an amount greater than 5% andless than 35%, and at least one of Cu in an amount greater than 3% andless than 35%, and Ag in an amount greater than 3% and less than 35%;and residual inevitable impurities, in which the high-entropy alloy hasa dual phase in which a Cr or a Cr-rich phase is distributed within amatrix of the high-entropy alloy in filament or ribbon form.

The high-entropy alloy may further include at least one of, by at. %, Tiin an amount of 0.02 to 5%, Zr in an amount of 0.02 to 5%, Hf in anamount of 0.02 to 5%, Mo in an amount of 0.02 to 5%, W in an amount of0.02 to 5%, Si in an amount of 0.02 to 5%, Al in an amount of 0.02 to5%, V in an amount of 0.02 to 5%, and Ta in an amount of 0.02 to 5%, andprecipitates may be formed in the matrix.

The high-entropy alloy having the dual phase may be a plate, rod, orwire product.

According to an aspect of the present disclosure, a method formanufacturing a high-entropy alloy includes: preparing a metallicmaterial, the metallic material including, by at. %, Cr in an amountgreater than 5% and less than 42%, Mn in an amount greater than 5% andless than 35%, Fe in an amount greater than 5% and less than 35%, Ni inan amount greater than 5% and less than 35%, and at least one of Cu inan amount greater than 3% and less than 35%, and Ag in an amount greaterthan 3% and less than 35%, and residual inevitable impurities;manufacturing an alloy with the prepared metallic material by melting(casting) or powder metallurgy; carrying out a homogenization heattreatment for the manufactured alloy; primarily processing thehomogenization heat treated alloy and then cooling it thus obtained;carrying out an intermediate heat treatment for the cooled alloy at atemperature of 350 to 600° C.; and secondarily processing theintermediate heat treated alloy so as to form a composite structure inwhich a Cr or a Cr-rich phase is distributed within a matrix of thealloy in filament or ribbon form.

The metallic material may further include at least one of, by at. %, Tiin an amount of 0.02 to 5%, Zr in an amount of 0.02 to 5%, Hf in anamount of 0.02 to 5%, Mo in an amount of 0.02 to 5%, W in an amount of0.02 to 5%, Si in an amount of 0.02 to 5%, Al in an amount of 0.02 to5%, V in an amount of 0.02 to 5%, and Ta in an amount of 0.02 to 5%, andprecipitates may be formed in the Cr filament-reinforced matrix throughthe intermediate heat treatment.

The method may further include, prior to the homogenization heattreatment of the melted (cast) alloy, rapidly solidifying (quenching)the melted (cast) alloy.

The homogenization heat treatment may be performed at a temperaturewithin a range of 600 to 1,200° C. for 1 to 48 hours.

The primary and secondary processing may be at least one of hot working,rolling, extruding, and room-temperature working.

At least one of the primary and secondary processing may be processingthe alloy into one of a plate, a rod, and a wire.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is schematic views illustrating microstructures of ahigh-entropy alloy before thermo-mechanical processing, and FIG. 1B isschematic views illustrating microstructures of a high-entropy alloywith Cr-rich filaments or second phase after thermo-mechanicalprocessing, according to an exemplary embodiment;

FIG. 2 is an image obtained by observing microstructures of InventiveExample 1;

FIGS. 3A and 3B are images obtained by observing microstructures ofInventive Example 8;

FIG. 4 is a process flowchart illustrating an example of a method formanufacturing a high-entropy alloy, according to an exemplaryembodiment; and

FIG. 5 is an X-ray diffraction (XRD) analysis graph of Inventive Example1.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the attached drawings.

The present disclosure may, however, be exemplified in many differentforms and should not be construed as being limited to the specificembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the disclosure to those skilled in the art.

The terminology used herein describes particular embodiments only, andthe present disclosure is not limited thereby. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises,” and/or “comprising”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, members, elements, and/or groupsthereof, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, members, elements, and/orgroups thereof.

Hereinafter, embodiments of the present disclosure will be describedwith reference to schematic views illustrating embodiments of thepresent disclosure. In the drawings, for example, due to manufacturingtechniques and/or tolerances, modifications of the shape shown may beestimated. Thus, embodiments of the present disclosure should not beconstrued as being limited to the particular shapes of regions shownherein, for example, to include a change in shape resulting frommanufacturing. The following embodiments may also be constituted aloneor as a combination of several or all thereof.

The contents of the present disclosure described below may have avariety of configurations, and only a required configuration is proposedherein, but the present disclosure is not limited thereto. Unlessotherwise indicated, elemental contents and ranges thereof are expressedby atomic percentage (“at. %”).

Hereinafter, exemplary embodiments in the present disclosure will bedescribed.

The inventors of the present disclosure conducted various research on amethod for increasing mechanical or physical properties, such asstrength and ductility, of a high-entropy alloy. As a result, when acomposition of a portion of various alloying elements is separated orforms other ductile phases, or when segregation or phase separationoccurs, instead of various alloying elements forming a solid solutionwith a single-phase face-centered cubic (FCC) or body-centered cubic(BCC) structure, the inventors have found that both the strength andtoughness were increased after the thermo-mechanical processing.Further, the inventors have confirmed that when a second phase (aCr-rich phase) present in the matrix is refined through powdermetallurgy or rapid solidification (quenching) in manufacturing thealloy, and furthermore when a fine filament structure is distributedthrough processing, a high-entropy alloy, having excellent levels ofstrength and ductility, may be formed, and have proposed the presentdisclosure.

The high-entropy alloy having the composite structure, according to anexemplary embodiment, may include, by at. %, Cr in an amount greaterthan 5% and less than 42%, Mn in an amount greater than 5% and less than35%, Fe in an amount greater than 5% and less than 35%, Ni in an amountgreater than 5% and less than 35%, and at least one of Cu in an amountgreater than 3% and less than 35%, and Ag in an amount greater than 3%and less than 35%, and residual inevitable impurities. A Cr or a Cr-richphase may be distributed as filament or ribbon form in a matrix of thehigh-entropy alloy

A composition of the high-entropy alloy, according to an exemplaryembodiment, will hereinafter be described in detail.

In an exemplary embodiment, Cr, Mn, Fe, Ni, and at least one of Cu andAg may be basic elements constituting the high-entropy alloy, may be thetransition metal group in period 4, and elements suitable to form asolid solution or the like because of the small difference in atomicradius, or the like.

Mn and Ni may be elements promoting a solid solution having a FCCstructure, Cr may have a BCC structure, when Cu or Ag is added, theCr-rich phase may be separated, and since the Cr-rich phase is changedinto the form of a filament during thermo-mechanical processing,mechanical properties may be increased.

In an exemplary embodiment, limiting the contents of Cr, Mn, Fe, Nielements to, by at. %, greater than 5%, and 35% or less, respectively,is to induce changes in partial entropy in equivalent composition thatmay significantly increase entropy as far as possible, but to preventthe contents from being beyond an entropy range for forming the solidsolution.

In addition, Cu may be an element inducing separation of the Cr-richphase in the matrix, which may increase ductility, and subsequent tothermo-mechanical processing, the Cr-rich phase may be elongated so asto form a filament, thus increasing strength. For example, the separatedFe—Mn—Ni—Cu (Ag) phase may have a FCC structure, the separated Cr-richphase may have a BCC structure, and different slip systems of the twophases may cause the Cr-rich phase to be extremely twisted duringthermo-mechanical processing, so as to form a filament having a ribbonshape, thus reinforcing the matrix.

In an exemplary embodiment, the reason for limiting the content of Cu togreater than 3%, and 35% or less, is to induce changes in strength andductility according to fractions of the separated phase, thus leading toincreases in ductility and strength due to the effect of adding analloying element.

In addition, the reason for limiting the content of Ag to greater than3%, and less than 35%, is to reinforcing the matrix without forming acomplete solid solution with Fe, Mn, and Ni. This may increaseductility, may allow an Ag-rich phase to be elongated afterthermo-mechanical processing, so as to form a filament, thus increasingstrength.

The high-entropy alloy, according to an exemplary embodiment, mayfurther include at least one of Ti in an amount of 0.02 to 5%, Zr in anamount of 0.02 to 5%, Hf in an amount of 0.02 to 5%, Mo in an amount of0.02 to 5%, W in an amount of 0.02 to 5%, Si in an amount of 0.02 to 5%,Al in an amount of 0.02 to 5%, V in an amount of 0.02 to 5%, and Ta inan amount of 0.02 to 5%. With the addition of these constituentelements, precipitates may be formed in the matrix. The precipitatesformed in such a manner may be uniformly distributed within the matrixto reinforce the matrix and hinder dislocation movement, thus increasingmechanical properties of the high-entropy alloy. The added alloyingelements may form fine precipitates in the matrix of thefilament-reinforced high-entropy alloy, and may further reinforce thehigh-entropy alloy, in addition to the increase in strength by thefilament.

The reason for limiting the contents of Ti, Zr, Hf, Mo, W, Si, Al, V,and Ta to 0.02 to 5%, respectively, is that when the contents are lessthan 0.02%, a precipitation hardening effect may be extremely less,whereas when the contents exceed 5%, the ratio of precipitates may beextremely high to degrade workability, causing brittleness.

FIGS. 1A and 1B are schematic views illustrating microstructures of thehigh-entropy alloy, according to an exemplary embodiment, and theexemplary embodiment will be described in detail, with reference toFIGS. 1A and 1B.

It is desirable that before thermo-mechanical processing, themicrostructures of the high-entropy alloy, according to an exemplaryembodiment, may have, for example, a second phase distributed within amatrix, which is a single-phase solid solution, as illustrated in FIG.1A. In the high-entropy alloy, according to an exemplary embodiment, forexample, a filament structure formed by elongation of the second phasehaving ductility, as illustrated in FIG. 1B, may be distributed withinthe matrix after thermo-mechanical processing.

In an exemplary embodiment, the matrix may mean a solid solution formedof elements such as Fe, Mn, Ni, and Cu.

The second phase may refer to all various forms or structures, such as asolid solution (a second solid solution) of a phase having otherelements, single-phase dendrites, segregation, a phase separationregion, and crystal grains. For example, the second phase may mean astructure different from the matrix. The high-entropy alloy, having thesecond phase distributed therein, may ensure excellent ductility.

The second phase may be a Cr-rich phase not fully dissolved in the solidsolution of the high-entropy alloy, and may have a higher level ofductility than the matrix, thus increasing ductility of the high-entropyalloy.

When the high-entropy alloy is processed by rolling, extruding, or thelike, cooled, subjected to an intermediate heat treatment, and formedinto a plate, a rod, or a wire, a Cr or a Cr-rich phase may be developedin filament or ribbon form to reinforce the matrix of the high-entropyalloy. For example, the high-entropy alloy may be a plate, rod, or wireproduct.

The second phase, as illustrated in FIGS. 2, 3A, and 3B, may beelongated after being processed to be present as a Cr-rich filamentelongated with a thickness of 0.05 to 2 μm and a length of 10 to 1,000μm, thus reinforcing the matrix. When present with a thickness of 0.05to 2 μm and a length of 10 to 1,000 μm, the Cr-rich filament may not bedamaged by deformation and may have optimized resistance to deformationto increase strength. The elongated composite phase may be present inthe matrix of the high-entropy alloy in Cr-rich filament or ribbon formto provide an interface present as an obstacle to deformation of thehigh-entropy alloy, thus increasing strength of the high-entropy alloy.

As a result, strength and ductility of the high-entropy alloy, having aCr-rich filament- or ribbon-shaped structure containing a precipitationphase in the matrix by the processing, may be simultaneously increased.

A method for manufacturing a high-entropy alloy, according to anexemplary embodiment, will be described in detail.

The method for manufacturing a high-entropy alloy may include: preparinga metallic material containing, by at. %, Cr in an amount greater than5% and less than 42%, Mn in an amount greater than 5% and less than 35%,Fe in an amount greater than 5% and less than 35%, Ni in an amountgreater than 5% and less than 35%, and at least one of Cu in an amountgreater than 3% and less than 35%, and Ag in an amount greater than 3%and less than 35%, and residual inevitable impurities; manufacturing analloy with the prepared metallic material by melting (casting) or powdermetallurgy; carrying out a homogenization heat treatment for themanufactured alloy; primarily processing the homogenization heat treatedalloy and then cooling it thus obtained; carrying out an intermediateheat treatment for the cooled alloy at a temperature of 350 to 600° C.;and secondarily processing the intermediate heat treated alloy so as toform a composite structure in which a Cr or a Cr-rich phase isdistributed within a matrix of the alloy in filament or ribbon form.

FIG. 4 is a process flowchart illustrating a schematic sequence ofmanufacturing processes, according to an exemplary embodiment.

As illustrated in FIG. 4, a metallic material may be preparedcontaining, by at. %, Cr in an amount greater than 5% and less than 42%,Mn in an amount greater than 5% and less than 35%, Fe in an amountgreater than 5% and less than 35%, Ni in an amount greater than 5% andless than 35%, and at least one of Cu in an amount greater than 3% andless than 35%, and Ag in an amount greater than 3% and less than 35%,and residual inevitable impurities.

The metallic material may further include, for example, at least one of,by at. %, Ti in an amount of 0.02 to 5%, Zr in an amount of 0.02 to 5%,Hf in an amount of 0.02 to 5%, Mo in an amount of 0.02 to 5%, W in anamount of 0.02 to 5%, Si in an amount of 0.02 to 5%, Al in an amount of0.02 to 5%, V in an amount of 0.02 to 5%, and Ta in an amount of 0.02 to5%.

Subsequently, an alloy may be manufactured with the prepared metallicmaterial, using melting (casting) or powder metallurgy.

The melting (casting) or the like may be performed to alloy the preparedmetallic material, an alloying method for the same is not limitedthereto, and the metallic material may be alloyed by a known method. Forexample, the alloy may be manufactured by casting, arc melting, orpowder metallurgy. The manufactured alloy may subsequently be cooled,but a detailed cooling method for the same is not limited, and slowcooling, and air cooling, or rapid solidification (quenching) may beused.

For example, a rapid solidification (quenching) method may be used tocool the melted (cast) alloy. This is because the second phase (theCr-rich phase) present within the matrix may be refined by thequenching, and hence mechanical properties may be increased.

Subsequently, the manufactured alloy may be subjected to ahomogenization heat treatment. The homogenization heat treatment may beperformed to induce diffusion, for example, at a temperature within arange of 600 to 1,200° C. for 1 to 48 hours.

Subsequent to the homogenization heat treatment, the alloy may becooled. The cooling method is not particularly limited, and an aircooling or furnace cooling method may be used.

The alloy subjected to the homogenization heat treatment may beprimarily processed and then cooled at room temperature. The primaryprocessing method is not particularly limited, and any known processingmethod may also be applied. The primary processing method may be atleast one of hot working, rolling, extruding, and room-temperatureworking. By the first processing method, as illustrated in FIG. 1B, thesecond phase within the high-entropy alloy may be changed into thefilament structure.

The cooled alloy may be subjected to an intermediate heat treatment at atemperature of 350 to 600° C. In such an intermediate heat treatment, aprecipitation phase, including at least one of Ti, Zr, Hf, Mo, W, V, Ta,Si, and Al, may be formed within the matrix of the alloy. Further, aportion of Cr-rich filament phases formed by the above-mentioned primaryprocessing method may be rendered spherical by recovery, and the Cr-richfilament phases rendered spherical may be elongated by a subsequentsecondary method.

Thus, precipitates formed within the matrix may be uniformly distributedwithin the matrix to reinforce the matrix, and may simultaneouslyincrease strength and ductility of the high-entropy alloy, together withthe second phase (the Cr-rich phase) formed to have the filament orribbon shape.

Ultimately, a composite structure, having a Cr or a Cr-rich phasedistributed within the matrix in fine filament or ribbon form, may beformed by secondarily processing the alloy subjected to the intermediateheat treatment.

The secondary processing method is not particularly limited, and anyknown processing method may also be applied. For example, the secondaryprocessing method may be at least one of hot working, rolling,extruding, and room-temperature working. By the secondary processingmethod, as illustrated in FIG. 1B, the second phase within thehigh-entropy alloy may be elongated into the filament structure.

At least one of the primary and secondary processing may be forming thealloy into one of a plate, a rod, and a wire.

The primary and secondary processing and the intermediate heattreatment, as described above, may allow the high-entropy alloyaccording to an exemplary embodiment to be simultaneously increased instrength and ductility.

Hereinafter, exemplary embodiments in the present disclosure will bedescribed in more detail through examples.

Example 1

Metallic materials, having compositions (at. %) as shown in Table 1below, were prepared, and were arc melted in a vacuum atmosphere andthen air cooled to manufacture high-entropy alloys according toComparative Examples 1 to 3 and Inventive Examples 1 to 9. Subsequently,the manufactured high-entropy alloys were subjected to a homogenizationheat treatment.

The high-entropy alloys manufactured in such a manner were cooled, andthen the high-entropy alloys according to Inventive Examples 1 to 7 weresubjected to primary hot rolling at a total reduction ratio of 75%, toan intermediate heat treatment at 450° C. for 2 hours, and to secondarycold rolling at a total reduction ratio of 95% to manufacture plateshaving a thickness of 1 mm. The high-entropy alloys according toInventive Examples 8 and 9 were subjected to primary hot rolling at atotal reduction ratio of 75%, to an intermediate heat treatment at 450°C. for 2 hours, and to drawing at a total drawing ratio of 99% tomanufacture wires having a diameter of 1 mm.

The high-entropy alloys according to Inventive Examples 10 and 11 hadincreased formability by refining second phases (Cr-rich phases) presentwithin matrixes by arc melting and then rapid solidification(quenching), and were subjected to primary hot rolling at a throughputof 75%, to an intermediate heat treatment at 450° C. for 2 hours, and tosecondary cold rolling at a total reduction ratio of 95% to manufactureplates having a thickness of 1 mm.

Tensile tests were performed on the plates and wires of the high-entropyalloys manufactured as described above, and mechanical propertiesthereof were estimated. The results of estimation are shown in Table 1.

TABLE 1 Cooling Tensile Yield Elongation Alloy type after strengthstrength percentage Classification composition Form Microstructurescasting (MPa) (MPa) (%) Comparative Co₂₀Cr₂₀Fe₂₀Mn₂₂Ni₁₈ Plate Singlephase Air 620 480 40 Example 1 cooling Comparative Fe₂₅Ni₂₅Co₂₅Cr₂₅Plate Single phase Air 1000 870 35 Example 2 cooling ComparativeFe₂₀Mn₂₀Ni₂₀Co₂₀Cr₂₀ Plate Single phase Air 760 640 17 Example 3 coolingInventive Fe₂₀Ni₂₀Cr₂₀Mn₂₀Cu₂₀ Plate Matrix + Cr-rich Air 1560 1420 30Example 1 filament cooling Inventive Fe₂₀Ni₂₀Cr₂₀Mn₂₀Ag₂₀ Plate Matrix +Cr-rich Air 1620 1550 27 Example 2 filament cooling InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.65)Cu₂₀Ag_(0.35) Plate Matrix + Air 1920 1780 28Example 3 Precipitation cooling phase + Cr-rich filament InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.65)Cu₂₀Ti_(0.35) Plate Matrix + Air 1850 1630 31Example 4 Precipitation cooling phase + Cr-rich filament InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.65)Cu₂₀Mo_(0.35) Plate Matrix + Air 1910 1820 24Example 5 Precipitation cooling phase + Cr-rich filament InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.65)Cu₂₀A_(10.35) Plate Matrix + Air 1740 1560 29Example 6 Precipitation cooling phase + Cr-rich filament InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.65)Cu₂₀Ta_(0.35) Plate Matrix + Air 1820 1590 25Example 7 Precipitation cooling phase + Cr-rich filament InventiveFe₂₀Ni₂₀Cr₂₀Mn₂₀Cu₂₀ Wire Matrix + Cr-rich Air 2350 2100 25 Example 8filament cooling Inventive Fe₂₀Cr₂₀Ni₂₀Mn_(19.65)Cu₂₀Ag_(0.35) WireMatrix + Air 2470 2180 23 Example 9 Precipitation cooling phase +Cr-rich filament Inventive Fe₂₀Ni₂₀Cr₂₀Mn₂₀Cu₂₀ Plate Matrix + Cr-richRapid 1610 1540 32 Example 10 filament cooling InventiveFe₂₀Ni₂₀Cr₂₀Mn₂₀Ag₂₀ Plate Matrix + Cr-rich Rapid 1720 1630 29 Example11 filament cooling

As shown in Table 1 above, the high-entropy alloys, according toInventive Examples 1 to 7, satisfying the composition according to anexemplary embodiment and including the matrixes containing precipitatesand Cr-rich filaments may have excellent strength, as compared to thoseaccording to Comparative Examples 1 to 3, and in particular, when formedinto wires, the high-entropy alloys, according to Inventive Examples 1to 7, may exhibit outstanding mechanical properties. The high-entropyalloys, according to Inventive Examples 10 and 11, having increasedformability by refining the second phases (the Cr-rich phases) presentwithin the matrixes by arc melting and then rapid solidification(quenching), may exhibit excellent mechanical properties, as compared tothose, according to Inventive Examples 1 and 2, manufactured by arcmelting and then air cooling.

FIG. 2 is an image obtained by observing microstructures of InventiveExample 1, and after the thermo-mechanical processing, the Cr-rich phasewas changed to a filament structure.

FIGS. 3A and 3B are images obtained by observing microstructures ofInventive Example 8. In detail, FIG. 3A is the image illustrating thelongitudinal microstructures, and depicts a ribbon-shaped structure.FIG. 3B is the image illustrating the microstructures in a formingdirection (for example, a transverse direction), and after thethermo-mechanical processing, the Cr-rich phase was changed to anelongated filament structure.

TABLE 2 Cr Mn Fe Ni Cu (at. %) (at. %) (at. %) (at. %) (at. %) Matrix9.52 17.75 13.07 15.47 44.20 Dendrite arm 54.17 10.17 28.25 5.53 1.87

Table 2 shows a summary of EDS analysis values measured from thedendrite arms and the matrix of Inventive Example 1. As shown in Table2, a large amount of Cr may be distributed within the dendrite arms, andthe Cu alloying element may be dominantly distributed within the matrixbetween the dendrite arms.

Further, the Ni and Mn alloying elements may be distributed even in thedendrite arms, but may be dominantly distributed within the matrix. Inthe matrix between the dendrite arms, Cu may be dominantly distributed,but high contents of other alloying elements, such as Fe, Mn, and Ni,may be distributed.

Thus, a main alloying element of the dendrite arms may be Cr, and mayinclude a significant amount of the Mn and Fe alloying elements.

Since melting temperatures of Cu and Mn are lower than those of Fe andCr, Cu and Mn may tend to be separated while being solidified at earlystage to be grown as Cu—Mn dendrites. A melting temperature of the Nialloying element may be higher than that of the Cu and Mn alloyingelement, but may have a high degree of solid solubility of Cu unlikeother alloying elements. Thus, the Ni alloying element may bedistributed within the matrix in an amount similar to that of a Cuphase.

Cu and Mn may form a solid solution at a high temperature higher than900° C., and when the content of Mn exceeds 20%, Cu and Mn may beseparated into two phases below 700° C. Since Cr has a higher meltingtemperature than other alloying elements, Cr may be first solidifiedduring solidification process, and may be separated into two phases.

FIG. 5 is a graph illustrating an X-ray diffraction (XRD) analysisresults of Inventive Example 1.

As illustrated in FIG. 5, the diffraction peaks may be indicated as FCC(111), FCC (200), and FCC (220), and the peaks of BCC (111) and BCC(200) may indicate the presence of the Cr-rich phase. Further, it can beseen that a separated phase of the FCC phase may be present in view ofpartial separation of the diffraction peak of (220) displayed on the XRDdata.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentdisclosure, as defined by the appended claims.

What is claimed is:
 1. A high-entropy alloy comprising: by at. %, Cr inan amount greater than 5% and less than 42%, Mn in an amount greaterthan 5% and less than 35%, Fein an amount greater than 5% and less than35%, Ni in an amount greater than 5% and less than 35%, and at least oneof Cu in an amount greater than 3% and less than 35%, and Ag in anamount greater than 3% and less than 35%; and residual inevitableimpurities, wherein the high-entropy alloy has a dual phase in which aCr or a Cr-rich phase is distributed within a matrix of the high-entropyalloy in filament or ribbon form.
 2. The high-entropy alloy of claim 1,wherein the high-entropy alloy further includes, by at. %, at least oneof Ti in an amount of 0.02 to 5%, Zr in an amount of 0.02 to 5%, Hf inan amount of 0.02 to 5%, Mo in an amount of 0.02 to 5%, W in an amountof 0.02 to 5%, Si in an amount of 0.02 to 5%, Al in an amount of 0.02 to5%, V in an amount of 0.02 to 5%, and Ta in an amount of 0.02 to 5%, andprecipitates are formed in the matrix.
 3. The high-entropy alloy ofclaim 1, wherein the high-entropy alloy, having the dual phase, is aplate, rod, or wire product.
 4. A method for manufacturing ahigh-entropy alloy comprising: preparing a metallic material, themetallic material comprising, by at. %, Cr in an amount greater than 5%and less than 42%, Mn in an amount greater than 5% and less than 35%, Fein an amount greater than 5% and less than 35%, Ni in an amount greaterthan 5% and less than 35%, and at least one of Cu in an amount greaterthan 3% and less than 35%, and Ag in an amount greater than 3% and lessthan 35%, and residual inevitable impurities; manufacturing an alloywith the prepared metallic material by melting (casting) or powdermetallurgy; carrying out a homogenization heat treatment for themanufactured alloy; primarily processing the homogenization heat treatedalloy and then cooling it thus obtained; carrying out an intermediateheat treatment for the cooled alloy at a temperature of 350 to 600° C.;and secondarily processing the intermediate heat treated alloy so as toform a composite structure in which a Cr or a Cr-rich phase isdistributed within a matrix of the alloy in filament or ribbon form. 5.The method of claim 4, wherein the metallic material further includes,by at. %, at least one of Ti in an amount of 0.02 to 5%, Zr in an amountof 0.02 to 5%, Hf in an amount of 0.02 to 5%, Mo in an amount of 0.02 to5%, W in an amount of 0.02 to 5%, Si in an amount of 0.02 to 5%, Al inan amount of 0.02 to 5%, V in an amount of 0.02 to 5%, and Ta in anamount of 0.02 to 5%, and precipitates are formed in the Crfilament-reinforced matrix through the intermediate heat treatment. 6.The method of claim 4, further comprising, prior to the homogenizationheat treatment of the melted (cast) alloy, rapidly solidifying(quenching) the melted (cast) alloy.
 7. The method of claim 4, whereinthe homogenization heat treatment is performed at a temperature within arange of 600 to 1,200° C. for 1 to 48 hours.
 8. The method of claim 4,wherein the primary and secondary processing is at least one of hotworking, rolling, extruding, and room-temperature working.
 9. The methodof claim 4, wherein at least one of the primary and secondary processingis to form the alloy into one of a plate, a rod, and a wire.